SUB-RETINAL PROSTHESIS USING MULTI-PHOTODIODE SENSING TECHNOLOGY

Abstract

Disclosed herein is a sub-retinal prosthesis using a multi-photodiode sensing technology. The sub-retinal prosthesis using a multi-photodiode sensing technology includes: a pixel array including a plurality of pixels of which k pixels are set as a unit group; and a digital controller controlling the pixel array to activate one of the k pixels as a stimulation electrode and activate the other k-1 pixels as return electrodes, wherein the unit group includes k photodiodes, a sensing circuit and a current driver, the sensing circuit outputs a stimulation parameter using currents each generated by the k photodiodes according to irradiation of light as an input, and the current driver outputs a stimulation current corresponding to the stimulation parameter.

Claims

1. A sub-retinal prosthesis using a multi-photodiode sensing technology, comprising: a pixel array including a plurality of pixels of which k pixels are set as a unit group; and a digital controller controlling the pixel array to activate one of the k pixels as a stimulation electrode and activate the other k-1 pixels as return electrodes, wherein the unit group includes k photodiodes, a sensing circuit and a current driver, the sensing circuit outputs a stimulation parameter using currents each generated by the k photodiodes according to irradiation of light as an input, and the current driver outputs a stimulation current corresponding to the stimulation parameter.

2. The retinal prosthesis of claim 1, wherein cathodes of the k photodiodes are connected to each other.

3. The retinal prosthesis of claim 1, wherein the sensing circuits and the current drivers are provided as many as the number of unit groups.

4. The retinal prosthesis of claim 1, wherein the k pixels include a central pixel and a plurality of peripheral pixels adjacent to the central pixel.

5. The retinal prosthesis of claim 1, wherein the k pixels include a central pixel and upper, lower, left, and right pixels adjacent to the central pixel.

6. The retinal prosthesis of claim 1, wherein the digital controller activates one of the k pixels as the stimulation electrode, and activates the other k-1 pixels as the return electrodes after a preset time has elapsed.

7. The retinal prosthesis of claim 1, wherein the unit group includes a power supply voltage, a plurality of switches connected to the power supply voltage, and capacitors each connected to the plurality of switches and the k photodiodes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIGS. 1A and 1B are views for describing a current bleeding phenomenon in a retinal prosthesis according to the related art;

[0028] FIG. 2 is a diagram illustrating a layout of stimulation/return electrodes for removing a current bleeding phenomenon;

[0029] FIG. 3 is a view illustrating a configuration of a retinal prosthesis according to an embodiment of the present disclosure;

[0030] FIG. 4 is a view illustrating a unit group of the retinal prosthesis according to an embodiment of the present disclosure;

[0031] FIG. 5 is a view illustrating a detailed configuration of a pixel array according to the present embodiment;

[0032] FIG. 6 is a diagram illustrating a detailed structure of a unit group pixel according to an exemplary embodiment of the present disclosure;

[0033] FIG. 7 is a view illustrating a case where a stimulation electrode and return electrodes are simultaneously activated by way of example;

[0034] FIG. 8 is a view illustrating a method in which the stimulation electrode is first activated to inject a current into the retina, and the return electrodes are then activated after a predetermined delay time; and

[0035] FIG. 9 is graphs illustrating measurement results of photodiode currents when a photodiode of 20 pm x 40 pm and a photodiode of 80 pm x 40 pm are irradiated with light with an illuminance of 0 to 3900 lux.

DETAILED DESCRIPTION

[0036] The present disclosure may be variously modified and have several embodiments, and thus, specific embodiments will be illustrated in the drawings and be described in detail.

[0037] However, it is to be understood that the present disclosure is not limited to a specific embodiment, but includes all modifications, equivalents, and substitutions without departing from the scope and spirit of the present disclosure.

[0038] FIG. 3 is a view illustrating a configuration of a retinal prosthesis according to an embodiment of the present disclosure.

[0039] As illustrated in FIG. 3, the retinal prosthesis according to the present embodiment may include a pixel array 300, a serial-to-parallel interface (SPI) 302, and a digital controller 304.

[0040] The pixel array 300 includes a plurality of pixels of which k pixels are set as a unit group. The k pixels are sequentially activated as a stimulation electrode according to a preset order, and k-1 pixels other than the pixel activated as the stimulation electrodes are activated as return electrodes.

[0041] According to the present embodiment, sensing accuracy is increased by sharing photodiodes of a plurality of return electrodes adjacent to the stimulation electrode as well as a photodiode of the stimulation electrode.

[0042] That is, the present embodiment uses a multi-photodiode sensing technology.

[0043] The SPI 302 stores external data as parallel data, and a period, a pulse width, and the like, of a signal to be supplied to the pixel array 300 are determined by the parallel data.

[0044] The digital controller 304 controls the pixel array 300 to activate one pixel included in each group of the pixel array 300 as a stimulation electrode and activate the other pixels of each group of the pixel array 300 as return electrodes after a preset time elapses, that is, after a predetermined time delay, to detect a stimulation current.

[0045] As illustrated in FIG. 3, the digital controller 304 may detect a stimulation current of a pixel sensed by light through a row decoder 310 and a column decoder 312.

[0046] FIG. 4 is a view illustrating a unit group of the retinal prosthesis according to an embodiment of the present disclosure.

[0047] FIG. 4 illustrates a case where five pixels are set as one group, such that five photodiodes are shared.

[0048] Hereinafter, a case of sharing five photodiodes will be described by way of example, but the present disclosure is not limited thereto.

[0049] Referring to FIG. 4, a unit group includes five photodiodes 400-1 to 400-5, and outputs a stimulation current using currents each output from the five photodiodes when the five photodiodes are irradiated with light.

[0050] The multi-photodiode sensing technology according to the present embodiment increases an area of the photodiodes by connecting the photodiodes disposed in the plurality of pixels belonging to one group to each other.

[0051] When five photodiodes are included in one group, an area of the photodiodes increases five times.

[0052] Therefore, a photodiode sensing operation may be performed even with a small amount of light, such that a patient using the retinal prosthesis may secure a field of view even in a dark environment.

[0053] FIG. 5 is a view illustrating a detailed configuration of a pixel array according to the present embodiment.

[0054] Referring to FIG. 5, five pixels are set as one group, and reference numerals 1 to 5 refer to the order of the pixels activated as the stimulation electrode.

[0055] Each unit group includes a central pixel and upper, lower, left, and right pixels adjacent to the central pixel.

[0056] FIG. 6 is a diagram illustrating a detailed structure of a unit group pixel according to an exemplary embodiment of the present disclosure.

[0057] Referring to FIG. 6, a plurality of photodiodes 400-1 to 400-5 included in the unit group are connected to a power supply voltage VDD through a plurality of switches G1 to G5.

[0058] When the switches are turned on, cathodes of the photodiode 400-1 to 400-5 are charged with the power supply voltage.

[0059] Thereafter, when the photodiode are irradiated with light, voltages of the cathodes of the photodiodes decrease in proportion to an amount of light, and photodiode currents I.sub.PD are generated to discharge parasitic capacitors CP of the photodiodes.

[0060] A sensing circuit 600 senses the photodiode currents to generate a stimulation parameter.

[0061] In more detail, when the parasitic capacitors are lowered to a predetermined value or less, a counter value of the sensing circuit 600 increases by 1.

[0062] The stimulation parameter generated as described above is supplied to a current driver 604, such that a stimulation current corresponding to the stimulation parameter is output.

[0063] According to the present embodiment, by connecting the cathodes of the photodiodes 400-1 to 400-5 of the five pixels to each other to configure a circuit, the sensing circuit 600 generates the stimulation parameter corresponding to the currents each generated by the five photodiodes. Therefore, the sensing circuit 600 may generate a counter value 5 times higher than a case of using a single photodiode, such that accuracy of light sensing may be further improved.

[0064] In a case of connecting the five photodiodes to each other as illustrated in FIG. 6, when the stimulation electrode and the return electrodes are simultaneously activated, there is a fear that current delivery may not be smooth due to narrow gaps between the stimulation electrode and the return electrodes.

[0065] FIG. 7 is a view illustrating a case where a stimulation electrode and return electrodes are simultaneously activated by way of example.

[0066] In order to solve such a problem, a method in which the stimulation electrode is first activated to inject a current into the retina, and the return electrodes are then activated after a preset time (delay time) has elapsed as illustrated in FIG. 8 may be used.

[0067] Here, the delay time may be variously set from several ps to thousands of μs.

[0068] In addition, if an amount of return current is limited, the stimulation current relatively slowly returns through the return electrodes after the stimulation current spreads to the retina, such that a retinal stimulation effect may be improved.

[0069] FIG. 9 is graphs illustrating measurement results of photodiode currents when a photodiode of 20 μm×40 μm and a photodiode of 80 μm×40 μm are irradiated with light with an illuminance of 0 to 3900 lux.

[0070] Photodiodes of a TSMC 180 nm general process were used. It can be seen that a photodiode current increases as a size of the photodiode increases and increases according to illuminance of the light with which the photodiode is irradiated.

[0071] According to the present embodiment, currents generated by all photodiodes included in the central pixel and a plurality of peripheral pixels adjacent to the central pixel are sensed, and thus, performance of the retinal prosthesis may be improved.

[0072] According to the present disclosure, it is possible to increase sensing accuracy by sharing the photodiodes disposed in the plurality of pixels adjacent to the pixel operating as the stimulation electrode to increase an area of the photodiodes.

[0073] In addition, according to the present disclosure, it is possible to minimize a current bleeding phenomenon even though the stimulation electrode and the return electrodes are disposed to be close to each other by applying a delay to activation times of the stimulation electrode and the return electrodes.

[0074] The above-described embodiments of the present disclosure have been disclosed for the purpose of illustration, various modifications, alterations, and additions may be made by those skilled in the art to which the present disclosure belongs without departing from the spirit and scope of the present disclosure, and it is to be considered that such modifications, alterations, and additions fall within the following claims.